Laundry dryers



March 6, 1956 J, A. ENGEL LAUNDRY DRYERS Filed Dec. 1'7, 195] HEATImoron r HEAT I MOTOR ON ON OFF OFF I NVEN TUE J. ANTHONY ENGEL.

BY H

ATT URNEY United States PatentO LAUNDRY DRYERS J. Anthony Engel,Syracuse, N. Y., assignor, by mesne assignments, to The MurrayCorporation of America, Detroit, Mich., a corporation of DeiawareApplication December 17, 1951, Serial No. 262,066

8 Claims. (Cl. 34--45} This invention relates to laundry dryers, andmore particularly to a control system and operating cycle therefor.

In dryers of the type described, there is generally employed a tumblingdrum for laundry operating in conjunction with air heating elements, andmeans for circulating or translating heated air through the drum,together with various independent thermostatic controls.

The present invention is directed to a system wherein a single manualcontrol is utilized for commencing a cycle of operations, and in which asingle thermostatic control is utilized for effecting over-allsubsequent control over the heating element, tumbling drum and aircirculation, whereby the various functions are commenced and terminatedin an eflicient, shortened cycle dependent on the minimum length of timerequired to reach various controlling temperatures.

The invention is further directed to a dryer control system particularlyadapted to effect drying to a large extent by evaporation induced byradiant heat, and in which air utilized for carrying off evaporatedmoisture is exhausted at a temperature not greatly exceeding roomtemperature, so as to minimize wastage of heat and avoid undue heatingof the surrounding air in which the dryer is located.

The above and other novel features of the invention will appear morefully hereinafter from the following detailed description when taken inconjunction with the accompanying drawings. It is expressly understoodthat ,the drawings are employed for purposes of illustration only andare not designed as a definition of the limits of theinvention,reference being had for this purpose to the appended claims.

In the drawings, wherein like parts are indicated by like referencecharacters:

Figure 1 is a front elevation of a laundry dryer with parts broken away,to which the control system is applied;

Figure 2 is a View of the control switch, partly in section, togetherwith the control circuit; and

Figure 3 is a temperature time chart efiected by the control switch. I

Referring to the drawings, there is shown in Figure 1 a cabinetstructure having mounted therein a substantially cylindrical casing 12within which is a perforate revolving laundry-containing drum 14. Thedrum 14 may be of the type commonly in use having an access door in thefront wall thereof in alignment with a front wall cabinet access door,such parts not being shown since they form no part of the invention.

The drum is adapted to be rotated at a tumbling speed by a motor 16through a belt drive 18. The casing 12 in an upper portion thereof isprovided with an electrical heating element 20 of the infra-red radianttype, and adjacent such element are a number of inlet louvres 22 topermit entrance of air from within the cabinet 10 into the casing 12.Air is withdrawn from the casing 12 through a duct 24 having acentrifugal blower 26, belt driven as at 28 by the motor 16. Airexhausted from the casing 12 is delivered to the surrounding atmospherethrough an exhaust port 30.

Control over the operation of the machine is made dependent upon thetemperature within the casing 12, through the employment of athermostatic device of the type, for example, comprising a sealed bulbconnected to a switch actuating expansion bellows. For this purpose, thesealed bulb 32 is located within the casing 12, such bulb beingconnected by a conduit 34 to a thermostatic control switch assembly 36located conveniently on an inclined rear cabinet panel 37. The controlswitch (see Figure 2) comprises a casing 38 having a front panel 49through which projects a push knob control 42, the knob being mountedupon a pin 44 slidable in a boss 46 on the inside surface of the panel40. Such pin is provided with a flange 48 adapted to engage a springcontact leaf 50, the contact leaf being adapted by movement of the knob42 inwardly to engage the contact leaf 52 to close an electrical circuitthrough contacts 51 and 53 for the purpose of energizing the heatingunit 20.

A spring-pressed ball detent 54 mounted in the boss 46 is adapted toengage an annular groove 56 in the pin 44, so as to hold the knob 42 inits inward position against the urge of the leaf spring 50. Thestructure thus described is adapted to close a circuit through a relaycoil 58 which in turn closes contacts 60 adapted to energize the heatercoil 25) by completing a connection to a standard source of supply of220 v. The thermostatic bulb 32 and the conduit 34 lead to a closedexpansion chamber 62 mounted inside the rear wall 64 of the casing 38,such chamber being of generally hat-shaped section. The rim flange 66 isadapted to bear against a casing partition member 68. Within the chamber62 is a sealed bellows 70 having an external flange 72 held against ashoulder 74 on the internal wall of the chamber 62, an annular sealingdisk 76 acting to rigidly hold the bellows in place with its flange 72in sealed engagement with the shoulder 74. 7 7 Slidably mounted throughan aperture 78 in the partition wall 68 is a sleeve member 8%) having arear shoulder 82 adapted to be engaged by the end wall 34 of the bellows7 (i, such sleeve being adapted to be resiliently held against thebellows by a coil compression spring 86 bearing against the shoulder 82and the partition 68. Threaded within the sleeve for adjustment purposeis a pin 88 having an insulating tip 90 adapted to bear against aresilient contact leaf 92. Such contact leaf carries a contact 93adapted to engage with a contact 94 mounted upon a bimetallic heatsensitive contact arm 96. The leaves 50, 52 and 92 are mounted upon aninsulating multiple bracket member 9.8 and the bimetallic member issupported upon an insulating bracket member 100. The bracket member isprovided with stops 192 and M4 to limit the permissible bending of thebimetallic arm and supports a low current resistance heating element 106positioned immediately adjacent the bimetallic arm. The bimetallic arm,when heated by the resistance unit 106, is adapted to be bent upwardlyso as to engage the stop 164.

The contacts 93 and 94 on the contact leaf 2 and bimetallic arm 96 areconnected to a solenoid Tilt; which in turn actuates switch contacts incircuit with the motor 16, such motor for convenience being connectedbetween one side of the 220 v. line and the neutral connection. Theresistance heater 106 is connected in parallel with the motor 16, sothat whenever the motor is energized, the

heating unit will heat the bimetallic arm 96, causing the same to movethe bimetallic arm 94 rearwardly into engagement with the stop 104. v

' it will be seen that the thermostatic bulb 32 is so arranged withinthe casing 12 as to be responsive to an increase in temperature withinthe casing. When the manual button 42 is moved inwardly to close thecircuit between the contact leaves 50 and 52, the infra-red heater isenergized and upon the temperature within the easing 12 reaching apredetermined temperature such as 170 F., the expansion of the fluidwithin the bulb 32 is sufficient to cause the bellows 70 to move the pin83 enough 'so as to in turn bend contact leaf 92 to close a circuitbetween contacts 93 and 94. Thus, the motor 16 within the casing whichwould tend to cause the motor starting contact 93 to separate from thecontact 94, cuting off the motor. In order to prevent such anoccurrence, the heater resistance 106 creates sufficient heat to causethe bimetallic arm 96 to move against the stop 104. By such means, themotor starting contacts 93 and 94 are biased and will remain closed,even though the bellows-actuated pin recedes slightly in response to adrop of temperature within the casing 12. In practice, a drop intemperature of 35-50 may be expected, and the bimetallic strip and itsstops are so correlated with to the thermostatically actuated bellows asto permit the motor to run until the temperature drops below 120 F.

V The tumbling of the clothes is effected by rotation of the drum 14-which is heated in its passage past the infrared heating coils 20. Bysuch an arrangement, the infra red heating coil 20 effects evaporativedrying action of the tumbling laundry by radiation primarily, and bycontact of the heated drum with the clothes. The blower 26 circulates ortranslates air through the drum at a low rate whereby to exhaust airfrom the drum as it accumulates moisture evaporated from the laundry.The laundry within the drum is preferably retained at a low temperature,for example, in the range of 135, to efiect an etficie'nt dryingoperation, it being appreciated that the higher the temperature of theair exhausted from the blower 30, the lower is the efficiency of theapparatus.

It will be highly desirable to have the air exhausted as little aboveroom temperature as possible, so as to minimize the heat lost merelythrough excess heating of the air circulated through the dryer. Thus theheat added to air entering through the louvres 22 by the heater 20 ispreferably equivalent to that consumed by evaporation within thetumbling drum. By utilizing a low rate of air flow, the entering air maybe heated to a higher temperahire, more effective for evaporativepurposes, and yet discharge at a low temperature.

So long as evaporation of moisture from laundry contained within thedrum continues, such evaporation acts to reduce the temperature of theair as it circulates therethrough. However, as the laundry approaches adry state, the rate of evaporation reduces, and the cooling effect ofsuch evaporation is substantially reduced, so that the temperaturewithin the casing tends to increase. When the laundry becomessubstantially dry, evaporation substantially discontinues, and when thisoccurs, the temperature Within the casing 12 rises at a relatively rapidrate, the rapid rate being in part due to the low rate of aircirculation. This factor is utilized to open the circuit to the heatingelement 20 to discontinue the drying operation. In order to effectthisresult, the pin 88 actuated by the thermostatic bellows 70 isadaptedto resiliently bow the contact leaf 92 into engagement with themanually operated push pin 44 moving the same sufficiently outward torelease the detent 54 so that the spring contact leaf will return themanual control 42 to the off position as shown.

At this point, the infra-red heating coil 20 is deenergized. The motor16, however, continues to run, tumbling the laundry within the drum anddrawing air through the casing, discharging the same through the outlet30. The temperature gradually decreases within the casing 12, and whenthe temperature drops to the thermostatic bellows has retractedsufficiently to cause the leaf contact 93 and 94 to separate, openingthe circuit to the motor 16 and the resistor 106.

In Figure 3, the temperature at the thermostatic bulb 32 is indicated bycurves illustrating a typical cycle. At the point 112, the temperaturehas risen to approximately 170", at which time the motor 16 isenergized. After this, there is a drop in temperature for the reasonspreviously set forth; the motor continuing to run, and the curvecontinues relatively flat at a temperature of or thereabouts for aperiod until substantially all the moisture is evaporated from thelaundry contained within the drum. Such point is roughly indicated as at114. The temperature thereafter rises to the value indicated at 116 whenthe infra-red heating coil 20 is de-energized, and thereafter, the motorcontinues to rotate the drum and draw air therethrough until thetemperature drops to a value indicated approximately at 118, or 120 F.,when the motor circuit is broken. The temperature at 118 is less thanthe temperature at the point 112 where the motor commences to operate byreason of the bias placed upon the contact 94 by the bimetallic arm 96.

It will be appreciated that any particular temperature limits foreffecting the operations described may be selected, it being the primaryobject of the invention to quickly build the infra-red radiation withinthe drum prior to commencing rotation and ventilation. Since the aheating coil 20 is located near the top of the drum, laundry in thebottom of the drum, when not rotating, is in a safe place, and will beprotected from undue heating effect during this period, even though thetemperature created within the drum is allowed to build up to a value inexcess of the operating temperature during drum rotation. Since it isdesirable to dry to a large extent by efiicient radiation and physicalcontact, rather than by excess heating of large amounts of air, it isdesirable to have the radiation effective before any forced circulationof air through the drum takes place. However, thereafter, thecirculation of air through the drum is suflieient to assist theevaporation of moisture by radiation by carrying off moisture atapproximately the rate of evaporation. It is not, however, desired toheat the air entering the drum to any substantial degree, other than forthe purpose of aidingevaporation and compensating for the cooling efiectof evaporation within the drum, and it is not desired to flowsubstantial quantities of air through the drum. Consequently,evaporation is balanced against the quantity of heat imparted to the airentering the drum so as'to maintain a relatively low temperature of theair being discharged. The air entering at a low volumetric rate isheated to provide the necessary heat value to be expended inevaporation.

Upon the near completion of the drying of the laundry, the temperaturerises substantially above the low temperature value referred to. Thistemperature rise serves as an indication that the drying operation iscompleted or substantially completed, and is utilized to discontinue theoperation of the infra-red heating coil, following which the drumrotation and air circulation is continued until the laundry is reducedto a temperature safe to handle without discomfort. It will beunderstood that the air flowing through the discharge outlet will bemorenear room temperature than the air at the bulb 32, and that the positionof the bulb may bevaried somewhat to provide an optimum controlsituation dependent on air temperature within the drum, as distinguishedfrom the temperature of freshly heated air in the immediate region ofthe heater element 20.

From the foregoing, it will be seen that provision is made for quicklybringing the apparatus to a temperature for effective drying before aircirculation commences, and that the drying time thereafter isautomatically controlled by the temperatures existing within the casing,resulting from the balance of evaporation and heat introduced by themoderate flow of air therethrough. With varying loads, the length ofdrying time is automatically varied in proportion. Although solenoids 58and 108 have been shown for closing the various power circuits, it willof course be understood that the contacts 51 and 53 and 93 and 94 may beinterposed in place of the solenoid contacts 60 and 110, if it bedesired to directly control the power circuits, and thereby eliminatesuch solenoids. Any safety thermostatic switch such as 120 may beinserted in the heater coil circuit. Such switch would only operateshould the temperature within the casing rise to a danger point due tofailure of the mechanism to function properly.

Although a single embodiment of the invention has been illustrated anddescribed, it is to be understood that the invention is not limitedthereo. As various changes in the construction and arrangement may bemade without departing from the spirit of the invention, as will beapparent to those skilled in the art, reference will be had to theappended claims for a definition of the limits of the invention.

What is claimed is:

1. In a laundry dryer, a housing, a rotatable tumbling drum containedtherein, means for rotating said drum, means for heating air within saidhousing, means for translating air heated by said heating means throughsaid drum and exhausting such air outside said housing, means foractivating said heating means, and means including a single thermostatfor activating said translating means only upon establishment of andduring the maintenance of a predetermined drying temperature in saidcabinet by said heating means, and deactivating said heating means uponestablishment of a predetermined temperature elevated above said dryingtemperature.

2. In a laundry dryer, a housing, a rotatable tumbling drum containedtherein, means for rotating said drum, electrical means for heating airwithin said housing, means for translating air heated by said electricalmeans through said drum and exhausting such air outside said housing, aswitch for closing a circuit to said heating means, and means includinga single thermostat for activating said translating means only uponestablishment of and during the maintenance of a predetermined dryingtemperature in said cabinet by said heating means, and deactvating saidheating means upon establishment of a predetermined temperature elevatedabove said drying temperature.

3. In a laundry dryer, a cabinet, a perforate rotatable drum containedtherein, including motor means for rotating said drum, electricalheating means within said cabinet, means for translating air throughsaid heating means and drum and in contact with fabrics containedtherein, and exhausting said air outside said cabinet, a switch forclosing a circuit to said motor means, a switch for closing a circuit tosaid heating means, said last-named switch having means for yieldinglyholding said switch closed upon actuation thereof, thermostatic meansresponsive to a temperature in said cabinet for closing said firstnamedswitch upon establishment of an effective drying temperature in saidcabinet, means for retaining said firstnamed switch closed through alimited range of temperature below the switch closing temperature andabove room temperature, and means establishing a connection from saidthermostatic means with said heating means switch for opening saidheating means switch upon establishment of a temperature elevated abovesaid drying temperature.

4. In a laundry dryer, a casing, a tumbling drum therein, a motor fordriving said drum, an air heater, and means driven from said motor fortranslating heated air through said drum and discharging such air intothe surrounding atmosphere, a switch manually movable for energizingsaid heater, a switch for energizing said motor, thermostatic meansacting in response to a predetermined temperature within said casing forclosing said motor switch whenever and only when the temperature withinthe casing reaches a predetermined drying temperature, said last-namedmeans acting to actuate said manually movable switch to de-energize saidheater upon a predetermined further increase in the temperature withinsaid casing, and means responsive to the closing of said motor switchfor establishing a temperature range below said predeterminedtemperature, and above room temperature during which said motor switchwill remain closed.

5. In a laundry dryer, a housing, a rotatable tumbling drum containedtherein, motor means for rotating said drum, electrical means forheating air within said housing, means actuated by said motor means fortranslating air heated by said electrical means through said drum andexhausting such air outside said housing, a switch for closing a circuitto said motor means, a switch for closing a circuit to said heatingmeans, said last-named switch having means for yieldingly holding saidswitch closed upon actuation thereof, thermostatic means for closingsaid first-named switch upon establishment of a predetermined dryingtemperature in said cabinet, for opening said heating means switch uponestablishment of a temperature elevated above said drying temperature,said air translating means being operative after the closing of saidfirst-named switch for establishing a lower temperature for opening saidfirst-named switch.

6. In a laundry dryer, a shell, a perforate tumbling drum within theshell, an electric motor for driving said drum, an air inlet for saidshell, an electric heater for the air inlet, an air outlet for saidshell, means driven by said motor for moving air through said inlet,through said shell, and out said outlet, a temperature-sensitive devicewithin said shell, an expansible chamber device associated with saidtemperature-sensitive device, a switch for energizing said electricheater, manually settable means for closing said switch and forming thesole means for closing said switch, means actuated by the expansiblechamber device for resetting said settable device to open said switchupon the existence of a predetermined maximum temperature within saidshell, a switch for said motor, and means actuated by said expansiblechamber device to close said switch and retain the switch closedwhenever the temperature-sensitive device exceeds a predeterminedminimum temperature, less than the predetermined maximum, and to opensaid switch when the temperaturesensitive device is below said minimum.

7. In a laundry dryer, a shell, a perforate tumbling drum within theshell, an electric motor for driving said drum, an air inlet for saidshell, an electric heater for the air inlet, an air outlet for saidshell, means driven by said motor for moving air through said inlet,through said shell, and out said outlet, a temperature-sensitive devicewithin said shell, an expansible chamber device associated with saidtemperature-sensitive device, a switch for energizing said electricheater, manually settable means for closing said switch and forming thesole means for closing said switch, means actuated by the expansiblechamber device for resetting said settable device to open said switchupon the existence of a predetermined maximum temperature within saidshell, a switch for said motor, means actuated by said expansiblechamber device to close said switch and retain the switch closedwhenever the temperature-sensitive device exceeds a predeterminedminimum temperature, less than the predetermined maximum, and to opensaid switch when the temperature-sensitive device is below said minimum,and means to lower the predetermined minimum temperature by a fixedincrement above which said motor switch remains closed subsequent toclosure thereof.

8. A laundry dryer comprising a tumbling drum, means for translating airthrough said drum, and means for driving said tumbling drum and saidtranslating means, means for heating the air drier to translationthrough said drum, a control device sensitive to the temperature of theair passing through said drum comprising a thermostatic bela 7 lows,including a plunger actuated thereby through a range of movement inproportion to the temperature'of said air, a motor switch actuated bysaid plunger and closed thereby during all movement of the plungerbeyond an initial portion of the range of movement thereof, a manualplunger aligned with said thermostatic plunger and having an end adaptedto abut against the end of said thermostatic plunger, means forestablishing a range of movement from said plunger from an off positionto an on position and a switch associated therewith and actuated therebyfor energizing said heating means, and adapted to be open or closed inaccordance with the corresponding position of said plunger, the onposition of said plunger placing the end thereof within the range ofmovement of the end of said thermostatic plunger, means for biasing saidplunger to the oil position, detent means for holding said plunger inthe on position with its end in the range of movement of the end of saidthermostatic plunger, whereby said thermostatic plunger upon reaching apredetermined maximum temperature will move said manual plunger from theon position, and release said detent for movement of the manual plungerto the otf position.

References Cited in the file of this patent UNITED STATES PATENTS2,296,063 Shaw Sept. 15, 1942 2,398,880 Broglie Apr. 23, 1946 2,467,525Cobb Apr. 19, 1949 2,524,438 Graves Oct. 3, 1950 2,564,867 Weber et a1Aug. 21, 1951 2,564,868 Weber et a1 Aug. 21, 1951 2,583,850 KautfmanJan. 29, 1952

